Jackson JSON 라이브러리 mapper.readTree 사용하기, Iterator 이용하기

Jackson JSON 라이브러리 mapper.readTree 사용하기

JsonNode myJsonNode = mapper.readTree(myJson); // String myJson값을 Json형태로 바꿔서

Iterator itr = myJsonNode2.getElements(); // Iterator를 사용해 요소를 객체로 저장한다.

import java.io.IOException;
import java.util.Iterator;
 
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.node.ObjectNode;
 
public class JacksonTest {
 
    public static void main(String[] args) throws JsonProcessingException, IOException {
     ObjectMapper mapper = new ObjectMapper();
     String myJson = "{\"a\":1990, \"b\":\"b is string\", \"c\": [{\"d1\":\"d1 is string\"}, {\"d2\":\"d2 is string\"}]}";
     
     myJson1(mapper, myJson);
     myJson2(mapper, myJson);
     
    }
    
    // 1. mapper.readTree 사용하기 
    private static void myJson1(ObjectMapper mapper, String myJson) throws JsonProcessingException, IOException {
        JsonNode myJsonNode = mapper.readTree(myJson);
        System.out.println("myJsonNode1:"+myJsonNode); 
        // myJsonNode1:{"a":1990,"b":"b is string","c":[{"d1":"d1 is string"},{"d2":"d2 is string"}]}
 
        if (myJsonNode.isObject()) {
            ObjectNode obj = (ObjectNode) myJsonNode;
            if (obj.has("c")) {
                 JsonNode valueC= obj.get("c").get(0).get("d1");
                 System.out.println("valueC Text값: "+valueC.getTextValue()); // valueC Text값: d1 is string
            }
        }
    }
    // 2. mapper.readTree와 Iterator 사용하기 
    private static void myJson2(ObjectMapper mapper, String myJson) throws JsonProcessingException, IOException {
        JsonNode myJsonNode2 = mapper.readTree(myJson);
        System.out.println("myJsonNode2:"+myJsonNode2); 
        // myJsonNode2:{"a":1990,"b":"b is string","c":[{"d1":"d1 is string"},{"d2":"d2 is string"}]}
 
        Iterator itr = myJsonNode2.getElements();
        
        while( itr.hasNext()) {
            JsonNode obj = (JsonNode)itr.next(); 
            System.out.println(obj);
        }
    }
}

[출력 결과]

myJsonNode1:{"a":1990,"b":"b is string","c":[{"d1":"d1 is string"},{"d2":"d2 is string"}]}

valueC Text값: d1 is string

myJsonNode2:{"a":1990,"b":"b is string","c":[{"d1":"d1 is string"},{"d2":"d2 is string"}]}

1990

"b is string"

[{"d1":"d1 is string"},{"d2":"d2 is string"}]